Early this year, Film Forum, the redoubtable revival house on West Houston Street, drew overflow crowds for a documentary about two elderly men squaring off over semicolons and commas. The film, “Turn Every Page,” starred the semicolon-deploying biographer Robert Caro and the semicolon-averse editor Robert Gottlieb, who for many years was the head honcho at Simon & Schuster and then at Alfred A. Knopf, and from 1987 to 1992 was the editor of The New Yorker. Their relationship—intense, wary, mysterious—lasted a half century. It began with “The Power Broker,” Caro’s biography of Robert Moses, which, to its author’s agony, Gottlieb trimmed by some three hundred and fifty thousand words.